Squad Designated Marksman Rifle

The Squad Designated Marksman Rifle, abbreviated SDM-R, is an American designated marksman rifle used by the United States Army. It is a heavily modified M16 rifle built to give a squad marksman more accuracy and reach, extending the effective range of an infantry squad to as much as 600 meters. The 3rd Infantry Division developed it alongside a Squad Designated Marksman training program, and the United States Army Marksmanship Unit built 240 rifles in house for deployment in Iraq, which is why it was informally called the AMU rifle. Builds used M16A2 or M16A4 lower receivers, a fluted stainless Douglas barrel, a free-floated rail handguard, a Harris bipod and a 4x32 ACOG optic. The design is similar in role to the SEAL Recon Rifle and the Mk 12 Special Purpose Rifle. The Army later replaced it, mostly because match grade 5.56 NATO ammunition performed well in the designated marksman role, and the H&K HK417-based M110A1 SDMR was slated to follow.